1. Field of the Invention
This invention relates to a semiconductor material especially suitable for use in forming a semiconductor layer on an insulator, for example, to make a device using the semiconductor layer.
2. Description of the Related Art
In the field of MOSLSI, technologies on SOI (silicon on insulator) are now being actively developed to meet the requirement of the use for lower source voltages. Heretofore, various methods for fabricating SOI substrates have been proposed, and some have been brought into practice. Today's typical methods for fabricating SOI substrates include a SIMOX process and a bonding process, but all involve the problems that it is difficult to control the thickness of the silicon (Si) film uniformly under 60 nm and the cost for fabricating the substrate is high, and these problems impede their wider practical use.
On the other hand, it is possible to make Si crystalline thin films on various kinds of substrates such as glass substrates by using the bonding process, but it becomes more and more difficult to ensure a uniform thickness of a film as the area for making the film becomes larger.
Moreover, although polycrystalline Si films can be readily formed on glass substrates or other various kinds of substrates, their electric characteristics are not satisfactory because of variance in grain size of crystal grains, existence of grain boundaries, randomness in orientation of crystal grains, and so forth.